The present invention relates generally to material handling systems and, more particularly, to controlling a vacuum generator arrangement for suction cups of material handling systems that are engaged with the objects and substantially sealed thereto via operation of the vacuum system comprising the vacuum generator arrangement and the suction cups. It is known to provide a material handling system that includes suction cups or the like that are adapted to be moved into engagement with an object, such as a substantially flat object or panel or the like, and to lift and move the object to a desired location. The suction cups may be moved into engagement with the object, and the vacuum generator may be actuated to create a vacuum between the object and a suction cup such that the object is retained to the suction cup as it is transported to the desired location. Such material handling systems may be a part of one or more working stations.
The vacuum generated at the suction cup(s) is provided by the vacuum generator arrangement in the vacuum system, whereby pressurized air is supplied or provided to the vacuum generator of the arrangement.
When the air supply to the vacuum generator is deactivated, such that no vacuum is generated, the vacuum in the vacuum system may dissipate through a vent that connects the vacuum system to an atmosphere outside of the system, and when the vacuum has dissipated in the system and in the cup, to a sufficient amount, the suction cup may be released from the object.
Prior art devices are known from e.g. EP-1064464 where it is disclosed a vacuum ejector pump for generating a negative pressure used for transportation or lifting purposes. And in, U.S. Pat. No. 7,950,422 where it is disclosed an auto-release vacuum device for a material handling system.
Vacuum systems for transporting objects involve one or more vents for activating vacuum generation in a gripper tool. Such a vent is electrically opened, e.g. by solenoid, for letting air through the vacuum generator to generate vacuum pressure in the gripper. It is mechanically closed e.g. by a spring device or magnet, letting no air through to the vacuum generator when at least a preset vacuum pressure is achieved and/or no vacuum pressure should be generated. When the vent is closed, no electric power is consumed by the vent. The vacuum system may therefore involve an Energy Saving (ES) function for saving energy by not powering vents of the vacuum system. Thus, control signals are used by a vacuum system controller for controlling the Energy Saving (ES) function. Said ES function makes use of vacuum pressure level settings defining a pressure interval wherein vacuum generation is only active when a minimum pressure level is detected and it is necessary to increase vacuum pressure up to a preset maximum pressure level where the vacuum generation is stopped.
According to prior art, the setting of the minimum pressure level parameter, ESLow, and maximum pressure level, ESHigh, is performed manually by an operator or user of a working station and it requires that the operator to take into consideration any fluctuation of the vacuum pressure over time in the gripper application that will affect the ability of the vacuum generator to reach a system vacuum pressure, i.e. system-pressure, pn− equal to or higher than ESHigh.
Thus, one drawback is that an operator has to set the threshold values ESLow and ESHigh manually for any gripper tool application of the working station. Further one drawback, or problem, is that the operator has to be very skilled and experienced to be able to set the threshold values ESLow, and ESHigh and to consider any fluctuation of the vacuum generation and pressure over time and many repeating working cycles WC in the gripper application.
The object of the present invention is to achieve an improved vacuum system that eliminates, or at least mitigates, the above stated drawbacks, by being more user-friendly to handle.